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BIOMECHANICS OF POSTURE
- 2. TO KNOW ABOUT POSTURE TO KNOW ABOUT DEFINITION TO ABOUT TYPES OF POSTURE TO UNDERSTAND ABOUT BIOMECHANICS OF POSTURE KINETICS AND KINEMATICS OF POSTURE BALACE AND POSTURAL CONTROL POSTURAL ANALYSIS AND EVALUATIONS ABNORMAL POSTURES
- 3. It is your power foundation- a stacked framework from your feet through your legs, hips, spine and shoulders to your head” Posture or position of greatest efficiency, around your center of gravity, with muscles on all sides, exerting pull.
- 4. Posture can be defined as the relative arrangement of different parts of the body with line of gravity.
- 5. In static postures the body and its segments are aligned and maintained in certain positions. Eg – Standing, kneeling, lying, and sitting
- 6. Dynamic posture refers to postures in which the body or its segments are moving—walking, running, jumping, throwing, and lifting.
- 7. The study of any particular posture includes kinetic and kinematic analyses of all body segments. Humans and other living creatures have the ability to arrange and rearrange body segments to form a large variety of postures, but the sustained maintenance of erect bipedal stance is unique to humans.
- 8. Perfect posture pays dividends- by reducing stress/loads which leads to tension in the antigravity musculature, degeneration of weight bearing structures, less efficient movement, misalignment and risk for injury.
- 9. Erect bipedal stance gives us freedom for the upper extremities, but in comparison with the quadrupedal posture, erect stance has certain disadvantages. Erect bipedal stance increases the work of the heart Places increased stress on the vertebral column, pelvis, and lower extremities Reduces stability
- 10. base of support (BOS), defined by an area bounded posteriorly by the tips of the heels and anteriorly by a line joining the tips of the toes, is considerably smaller than the quadruped base.
- 11. center of gravity (COG), which is sometimes referred to as the body’s center of mass, is located within the body approximately at the level of the second sacral segment, a location that is relatively distant from the base of support
- 12. Without appropriate neuromusculoskeletal compensation and accommodation, such actions result in imbalance and often falling. Thus, postural deviations resulting in balance problems lead to frequent strain and injury to antigravity structures.
- 13. one's entire weight can be considered as concentrated at a point where the gravitational pull on one side of the body is equal to the pull on the other side. This point is the body's center of gravity, and it constitutes the exact center of body mass When the center of gravity is above the base of support and the pull of gravity is successfully resisted by the supporting members, an equilibrium of forces or a state of balance is reached and no motion occurs.
- 14. center of gravity is located in the region just anterior to the top of the second sacral segment; ie, about 55% of the distance for women and 57% for men, from the plantar surfaces to the apex of the head in the erect position. Its location will vary somewhat according to body type, age, and sex, and move upward, downward, or sideward in accordance with normal position movements and abnormal neuromusculoskeletal disorders.
- 15. The accumulation of fat and the loss of soft tissue tone are common factors in altering one's center of gravity. Thus, the center of gravity shifts with each change in body alignment, and the amount of weight borne by the joints and the pull of the muscles vary within reasonable limits with each body movement. Adequate compensation is provided for in the healthy, structurally balanced person.
- 16. LINE OF GRAVITY Reference Points. The vertical A-P line of gravity of the body, as viewed laterally in the erect model subject, falls from above downward through the earlobe, slightly posterior to the mastoid process, through the odontoid process, through the middle of the shoulder joint, touches the midpoint of the anterior borders of T2 and T12, then falls just slightly anterior to S2, slightly behind the axis of the hip joint, slightly anterior to the transverse axis of rotation of the knee (slightly posterior to the patella), crosses anterior to the lateral malleolus and through the cuboid-calcaneal junction to fall between the heel and metatarsal heads. When viewed from the back, the lateral line of gravity passes through the occipital protuberance, the C7 and L5 spinous processes, the coccyx and pubic cartilage, and bisects the knees and ankles. Thus, the A-P and lateral lines of gravity divide the body into four quarters (Fig. 4.6). Plumb Line Analysis. The plumb line, as used in postural analysis, serves as a visual comparison to the line of gravity. For example, when the plumb line is centered over S1, it should fall in line with the occipital protuberance. In uncompensated scoliosis, however, it will be seen to fall lateral to the occipital protuberance.
- 17. BODY BALANCE AND EQUILIBRIUM Active and Passive States. Positions of the body that require muscular forces to maintain balance are said to be in active equilibrium, while those that do not require muscular effort are in passive equilibrium. In passive equilibrium, all segmental centers of gravity and the centers of all joints fall within the gravity line of the body which must fall within the base of support. This requires complete neutralization of all linear and rotary components of gravitational force by joint surfaces and the base of support. Thus, such a state is impossible in the erect position but possible in the horizontal position. Balance. When the forces of gravity on a body are in a balanced position, the pull is equal on all sides about the center of gravity; ie, its center of gravity is directly above its base of support and the body is quite stable (Fig. 4.7). The amount of body mass outside this base does not affect the equilibrium unless the center of gravity of the mass is altered. If a part is laterally shifted to one side without a compensatory shift of another part of equal weight, the center of gravity is displaced sideward. The body will topple if the center of gravity is displaced outside its base of support because gravity pulls greater on the side of weight displacement. Because males generally have a larger thorax, broader shoulders, and heavier arms than females, they are toppled with less force than are females of the same size.
- 18. Common Torques. In the body, all partial centers of gravity or their axes of motion do not coincide with the common line of gravity. In fact, many partial centers are quite distant from the common line, and this causes active rotary torques in many joints because of gravitational pull which must be neutralized by antigravity muscles. A weight-bearing joint is considered to be in equilibrium if the gravity line of the supported structure is equal to the joint's axis of rotation. If the gravity line is posterior to the joint's axis of rotation, the superior segment tends to rotate posteriorly in compensation. If it is anterior to the axis, the superior segment tends to rotate anteriorly. Toppling Rate. The rate of movement of an unbalanced body which is toppling depends on the amount of lateral displacement of the center of gravity from its base of support. For this reason, a toppled tree falls slowly at first because of trunk resistance and then rapidly as its center of gravity is further displaced from the tree trunk. A tall person falls harder than a short person. For the same reason, the further the body's center of gravity is displaced from the midline of its base of support, the more force is necessary to return it to the balanced position.
- 19. Aging- your body gradually loses its capacity to absorb and transfer forces however its not aging that influences posture as does: Inactivity/sedentary living/reluctance to exercise -leads to loss of natural movement flow, Poor postural habits -eventually becomes your structure, Biomechanical compensation → muscle imbalance, adaptive shortening, muscle weakness & instability within the “core”, Body composition – increases load, stresses on spinal structure, leads to spinal deviation, Workspace –ergonomics, Poor movement technique/execution/training , Injury -leads to reduced loading capacity or elasticity, Others:
- 20. Weight Bearing. The most economical use of energy in the standing position is when the vertical line of gravity falls through a column of supporting bones. If the weight-bearing bony segments are aligned so that the gravity line passes directly through the center of each joint, the least stress is placed upon the adjacent ligaments and muscles. This is the ideal situation, but it is impossible in the human body because the centers of segmental links and the movement centers between them cannot be brought to accurately meet with a common line of gravity. Stability. Since the body is a segmented system, the stability of the body depends upon the stability of its individual segments. The force of gravity acting upon each segment must be individually neutralized if the body as a whole is to be in complete gravitational balance. That part of balance contributed by an individual segment is called the segment's partial equilibrium, as contrasted with the total equilibrium of the whole body. Thus, each segment has its own partial center of gravity and partial gravity line. Position Changes. Any change in position of a partial center of gravity produces a corresponding change in the common center of gravity. When the arms are raised overhead and lowered, the center of gravity is respectively raised and lowered within the body. When the arms are stretched forward or backward, the center of gravity is respectively moved anteriorly or posteriorly within the body. When the trunk is flexed severely forward or laterally, the center of gravity shifts outside the body.
- 22. Alignment May be tight May be weak Exercises Mid back flexion Upper abdominals Thoracic extensors Mid and lower trapezius Active & passive thoracic extension Protracted scapulae Serratus anterior Shoulder adductors Shoulder internal rotators Mid & lower trapezius Rhomboids Stretch Serratus Stretch Pectoralis minor Narrowed intercostal spaces Intercostals Deep breathing Multifidus Quadratus lumborum Titled scapulae Pectoralis minor Lower trapezius Stretch Pectoralis major Stretch Latissimus dorsi Elevated scapulae Upper trapezius Levator scapulae Lower trapezius Strengthen Middle & lower trapezius Stretch Upper traps & Levator Extreme neck extension’ (Hyperextension) Long Cervical Extensors Short neck flexors Strengthen neck flexors
- 23. Alignment May be tight May be weak Exercises Anterior tilt Hip flexors Abdominals Stretch hip flexors Strengthen obliques for stabilization Avoid full sit ups Hip flexion Hip extensors Strengthen gluteals Extreme low back extension (hyperextension) Low back extensors Stretch low back extensors
- 24. Alignment May be tight May be weak Exercises Posterior Pelvic tilt Hamstrings Stretch hamstrings Low back flexion Back extensors Strengthen back extensors Hip extension Hip flexors Strengthen hip flexors
- 25. Alignment May be tight May be weak Exercises Posterior pelvic tilt Hamstrings Hip flexors Stretch hamstrings Strengthen hip flexors Long kyphosis Upper abdominals External obliques Upper back extensors Strengthen upper back extensors Stretch and strengthen abdominals Narrowed intercostal spaces Intercostals Deep breathing Hip extension Strengthen hip flexors Extreme neck extension (Hyperextension) Upper trapezius Levator scapulae High cervical extensors Neck flexors Stretch upper traps & levator, strengthen mid & lower traps, strengthen neck flexors Extreme knee extension (Hyperextension) Hamstrings Calf Strengthen hamstrings and calf
- 26. 1. Static Postural Assessment 2. Dynamic Postural Assessment 3. Gait analysis 4. Flexibility assessment 5. Muscle testing Once postural alignment is assessed the focus should be on teaching and training “Neutral Spine”
- 27. Standing on both feet: front, side and rear views Standing on one leg Sitting supported and unsupported Kneeling Supine Sleeping
- 29. Performing: A push- up A squat- with arms in front, lifting overhead A lunge Walking Lifting